Motor control system



Nov. l1, 1941. B. o. AUSTIN 2,262,379

4 MOTOR CONTROL SYSTEM Filed July 26, 1940 riff.

1% )Z M y 34564077 @Hast/2z Patented Nov. 11, 1941 UNITED STATES PATENT OFFICE Westinghouse Electric It Mannfact uring Company, East Pittsburgh, Pa., a corporation oi vania Pennsyl Application July 26, 1940, Serial No. 347,689

7Claims.

A more speciilc object oi my invention is to l0 provide i'or lcontrolling the dynamic braking of a vehicle by means of dual controllers which are operated in a predetermined sequence.

Another object oi my invention is to proportionately divide the dynamic brake between two l5 controllers, which may be pedal A further object of my invention is to correlate the dynamic brake and the mechanical or iluid brake systems on a vehicle.

Still another object of my invention is to pro- 20 vide for utilizing a current limit. relay for dual purposes in a motor control system.

'Other objects of my invention will be explained fully hereinaiter'or will be apparent to those skilled in the art.- 25

In practicing my invention, the dynamic braking is so divided between the power controller and the brake controller that the ilrst application oi dynamic braking is obtained when-'the collectors Ii and I0, respectively; a pair ot switches BI and B2 for establishing dynamic braking connections for the motor, and a switch H for connecting the ileld winding I2 across the power conductors I3 and Il during a portion oi the dynamic braking cycle to ensure that the dynamic braking action oi' the motor .builds up quickly.

In order to control the motor current during the accelerating and dynamic braking periods, a resistor R is provided which is shunted from the motor circuit. step-by-step. by means oi resistor shunting switches RI, R2, RI, R8, R'I and Rl which are actuated in sequential relation, as shown in the sequence chart in Fig. 2, during both the accelerating and the braking cycles. A vpair oi ileld shunting switches FI and F2 are provided for shuntlng the field winding I2 through-a'reactor I7 anfd a resistor Il in order to secure maximumspeed of themotor Il in a mannerzwell .known in the art.

As-shown, the actuatlngacoil oi the switch FI is soconnected across'the amature II when the dynamic brakingconnections are established that the-energinticnxoi the coil is proportional to thexvoltage generated' by the armature. There lore theswitchgFi is responsive to the speed or themotortrand. thejoperation oi therswitch is a function ofthe motor speed. In this manner adpower controller is returned to its' normal or .30' ditional'shunting oi the ileldzwinding is obtained oil posilon. The dynamic braking is increased by the initial.v movement oi the air brake pedal or controller, which changes the energization of a coil on a current limit relay, thereby changing the setting oi the relay to increase the braking current. The limit elayalso functions to deenergize a portion of the control edliime'nt at the end of the accelerating and the braking cycles.

AFor a fuller understanding ot the nature and objects oi my invention. reference may be had to the following detailed description, taken incon- Iiunction. with tlie accompanying drawing. in which:

`Figuren is a diagrammatic view oi a control system embodying my invention. and y Fig. 2 is a chartslowing the sequence oi operation of`- a portion oi the equipment illustrated in Pig. l.

Referring tothe drawing. the system shown therein comprises a motor iI-haringv au armature winding II andafseries eldwinding I2; a

`line switch LS and a switch Mior connectingthe motorto power conductors It'andll, thereby at` high motor speeds, thereby reducing the current gmeratei in the amature when dynamic vbraking is applied during high speed operation.

In'- order that the Asequential operation of the -36 resistor shuntingswitches may be controlled by interlock` progression with a relatively iew numberoiinterlock's on theseswitches. each switch is provided'with a closing coil and a holding coil. The closing coll is energized to close the switch 4.0 aitergwhich' the holding coil is energized to re- 'tain the switch in the closed position, it being unnecessary to maintain the closing coil energized aiter the holding coil becomes energized.

In accordance with the usual practice, the pro- ,45 man sia the resistor immun; switches, beth acceleration dynamic braking, is automatically controlled by a current limit relay LR', thereby preventing an excessive amount ot current owing through lthe motor windings. 'l'he relayLRisprovided with theusualseries coil winding Il which is connected in the armature circuit for the motor Il ad a calibrating winding 2l which is connected across the armature winding II oi the motor through an intersuwlvingswertotne'mewr mwen comme xoekziontnsswnenardunnsdynsmmbnxlay LR is also provided with a shunt winding 22 which is energized when the control has completed its sequence of operation, either during the accelerating or the braking cycles. The excitation o'i the shunt coil 22 causes the limit relay to be held in the open position. The holding il the limit relay in the open position disconnects al1 the closing coils of the resistor shunting switchas and the iield shunting switch F2 from the line and only the holding coils remain energized after the control sequence is completed. As is fully described in my copending application Serial No. 347,687, led July 26, 1940, the energization of the coil 22 is controlled by interlocks provided on the resistor shunting switches and the field shunting switch F2. In this manner the temperature of the closing coils is materially reduced since they are no longer continuously energized and, furthermore, a saving in the energy required to operate the control equipment is effected.

In the present system the coil 22 on the relay LR is also utilized to change the dynamic braking eiect of the motor IU. The ilrst application of the dynamic brake is obtained by returning a master'controller MC to its normal or ofi position, in which position the dynamic braking connections are established, as will be explained more fully hereinafter. The second application or increase of the dynamic brake is obtained on the initial movement of a-brake controller BC which also may be utilized to control the operation of the air brake system (not shown).

When the controller MC is in the braking position, the maximum amount of braking at this vposition'is determined bya resistor 23 which is connected' in series circuit relation with the coil 22 on the relay LR. when the controller BC is,in the "oiI position. In this manner the coil`22 is energized from the power conductors I2 and I4 and is accumulative with the series coil I9 on the limit relay, thereby lowering the setting of the relay. The relay in turn governs the amount of braking current permitted to ow by controlling the operation of the resistor shunting switches which shunt the resistor R from the motor circuit. Y

Ii it is desired to increase the braking rate, the controller BC is actuated from the "oi'i position. The initial movement of the controller causes the energizing circuit for the coil 22 to be interrupted. The deenergization of this coil raises the setting of the limit relay which, in turn.

asesino 'coasting position, and then through the accelerating positions, the maximum speed of the vehicle being obtained by actuating the controller to the fullv power position at which time the permits a higher braking rate. In this manner-V the dynamic braking is proportionately divided between the power pedal and the brake pedal. Furthermore, the shunt coil 22 on the relay LR is utilized for the dual purposes of deenergizing the closing coils of the resistor shunting switches at the end o! the accelerating and the braking cycles, as explained hereinbeiore, and for chang-l ing the dynamic braking rate yduring the brakin! cycle. d l -v As described in my foregoing copending application, dynamic braking, coasting and accelerating or application of power to the vehicle are all controlled by the controller MC which .utilized for dynamic braking, another portion for switch'F2 is closed to shunt the neld winding of the motor. Beginning at the full power position, the ilrst initial motion of the controller in the backward direction changes the motor from short iield to full iield. Further movement towards the coasting position begins to insert resistance in series with the motor. thereby softening the shut-oir of power. Passing through the coasting position, at which time the motor is disconnected from the power conductors, the rst braking point is then obtained. The resistor R. is shunted from the motor circuit by the resistor shunting switches, which are under the control of the limit relay LR, thereby maintaining a certain braking rate. Ii it is desired to increase the braking rate the controller BC is actuated to deenergize the coil 22 on the limitrelay, as explained hereinbeiore.

In order that the functioning of the foregoing equipment may be more clearly understood the operation of the system will be described in more detail. e Assuming that it is desired to accelerate the vehicle at the'maximum rate, the controller from standstill, nothing happens as the controller is moved through the braking and coasting positions.

When the ilrst acceleratingposition is reached the switches IS. Rl and M areclosed to connect the motor across the power conductors I2 and Il in series with the resistor R. The energizing circuit for the closing Vcoil of the switch LS may be traced from the power conductor Il throughv the current collector I5, conductor. contact members 26 and 21 on the controller MC, conductor 28, an interlock 29 on the switch BI, conductor 3i, the actuating coil of the switch LS, conductor 32 and the current collector il to the negative conductor I4. circuit for the switch M extends from the conductor 3| through the actuating coil oi the switch M to the negativeconductor 32.

Following the closing o! the switch LS the closing coil of the switch RI is energized through a circuit which may-be traced from the previously energized conductor 2B through an interlock. 33 on the -switch IS. conductor 34, an interlock 35 on the switch R1, conductor 3i, the closing coil of the switch Rl, conductor l1 and Vthe contact members of the relay LR to the negative conductor I2. Following the closing of the switch Rl, the holding coil of this switch 1 one step of the"resistor R from the motor cirkcuit.

be ofthe cam type, and pedal or foot-operated- The energizing circuit for the switch R2 may be traced from the previously energized conductor 26 through an interlock I9 4on the switch RI,v conductor Il, contact vmembers t2 on the controller MC,l conductor 4,3,lthe' closing v vcoil ofv the switch R2, conductor lI1 andv the contact members of the relay LR to the negative conductor 32.. The holding coil oi the switch The energizing` R2 is energized through an interlock 44 on the switch when it is actuated to the closed position.

Following the closing of the switch R2, the switches R3, R6, R1 and R3 are closedby interlock progression in a manner well known in the art. As shown in the sequence chart, the switches RI, R2, R3 and R6 are opened upon the closing of the switch R1. Thus the resistor R is connected in the motor circuit in two parallel pat-hs, and the switches R2, R3, R6 and RI are reclosed in the order shown in the sequence chart to shunt the resistor completely from the motor circuit. Since lthe operation of the resistor shunting switches by interlock progression under the control of the limit LR is well known in the railway control art, it is believed to be unnecessary to trace all the control circuits Ior these switches in detail.

As previously explained, the eld shunting switch F2 is closed at the end of the accelerating cycle to shunt the eld winding I2 through the reactor I1. The energizing circuit for the closing coll of the switch F2 may be traced from the previously' energized conductor 34 through contact members 45 oi' the controller MC, conductor 46, an interlock 41 En' the switch R8, conductor 4B, an interlock 49 on the switch RI, conductor 5I, an interlock 52 on the switch M, conductor 53, the closing coil of the switch F2, conductor 31 and the contact members of the relay LR to their negative conductor 32. The holding coil of the switch F2 is energized through an interlock 55 when the switch is closed.

As explained hereinbei'ore, the coil 22 of the relay LR is energized at the end of the accelerating cycle to open the contact members of the limit relay, thereby deenergizing the closing coils on the resistor shunting switches and the switch F2. The energizing circuit for the coll 22 may be traced from the previously energized conductor 28 through the interlock 29 on the switch BI, conductor 3l, an interlock 56 on the switch F2, conductor 51, a resistor 53, and the coil 22 to the negative conductor 32. In this manner the closing coils are deenergized to prevent overheating ot these coils. However, the resistor shunting switches and the ileld shunting yswitch F2 are maintained closed by the holding coils during operation of the vehicle. It will be understood that the holding coils require less current than the closing coils since it is only necessary for them to retain the switches in the closed position after they have once been closed by the closing coils.

When it is desired to decelerate the vehicle by means of dynamic braking. the controller MC is returned to the normal or braking position. It will be understood that the motor is disconnected from the power source when the controller is passing through the coasting position since all of the control equipment is deenergized. When the controller reaches the braking position, the switches RI, BI, B2 and H are closed. The

switches RI, BI and B2 establishl a dynamic braking circuit for the armaturey of the motor through the resistor'R, and the switch H, in conjunction with the switch BI', connects the ileld winding I2 of the motor across the power conductors to excite the ileld winding, thereby causing a rapid build-up of the motor current to assure a quick braking eiIect.

The energizing circuit for the switch B2 may be traced from the conductor 25 through the contact members 2E and 6I ot the controller MC, conductor 32, an interlock 63 on the switch M,

conductor 33, the closing coil of the switch Rl,l

conductor 31 and the contact members oi' the relay LR to the negative conductor 32. The energizing circuit for the coil of the switch H extends-from the previously energized conductor 68 through an interlockv 83 on the switch RI, conductor 1I, and the coll 4oi the switch H to the negative conductor 32.

The resistor shunting switches R2', R3, RI, and R3 are closed in the order shown in the sequence chart to shunt the resistor R from the motor circuit in the same manner as duringv` acceleration of the vehicle, the operation of switches being automatically controlled by limit relay LR. At this time the coil 22 on t? 2 relay LR is energized thereby lowering the ting of the relay. The energizing circuit for i: coil 22 may be traced from the power conduc i 25 through contact members 26 and 6I of if: i controller MC, conductor 52, the resistor contact members 12 o! the controller BG, ductor 13, the resistor 58 and the coil 22 to the negative conductor 32.

Ii.' it is desired to increase thebraking raze, the coil 22 is deenergized by actuating the con troller BC to the on position thereby opening the contact members 12 of this controller. In this manner the setting of the relay LR is raised and the braking current is increased by so controlling the operation of the resistor shunting switches-that a higher braking current, and consequently a higher braking rate, is permitted.

As explained hereinbefore, the coil 22 of the relay LR is energized at the end of the braking sequence, that is when the operation of the rem sistor shunting switches is completed, regardless of whether or not the controller BC has been operated in the foregoing manner to deenergize the coil during the braking cycle. The energiz ing circuit for the coil 22 at this time may be traced from the previously energized conductor 5I through an interlock 14 on the switch BI, conductor 13, a resistor 53, and the coil 22 to the negative conductor 32. In this manner the relay LR is actuated to its raised position to deenergize the closing coils of the resistor shunting switches.aijter they have completed their sequence oi operation during dynamic braking, in the same manner las during acceleration.

From the foregoing description it is evident that I have provided a control system which makes it possible to so proportion the dynamic braking of a vehicle between the power controller and the air brake controller that a normal braking rate is obtained by operating only the power controller. and the maximum braking rate is obtained by operating the brake controller in conjunction with the power controller. Thus, under normal operating conditions the braking controller is not utilized until it is desired to apply the uid or mechanical brakes, but under unusual conditions the braking controller may be utilized to increase the dynamic braking rate. Furthermore. the control system is simplified by utilizing the same coil on the limit relay to vary the braking rate and also to operate the relay to deenergize a portion of the control equipment at the end of the operating cycles.

`Since numerous changes may be made in the above described construction and diiIerent embodiments of the invention may be made without departing from the spirit and scope thereof, it is intended that all matter contained in the i'oregoing description or shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense.

I claim as my invention:

l. In a motor control system, the combination with a motor and a source of power therefor, of switching means for connecting the motor to the power source, additional switching means for establishing dynamic braking connections for the motor, and a controller for controlling the operation of said switching means, said controller being actuated from a normal or braking position through coasting and accelerating positions in sequential relation to accelerate the motor and from an accelerating position through the coasting and braking positions to decelerate the motor by dynamic braking.

2. In a motor control system, the combination with a motor and a source of power therefor, of switching means for connecting the motor to the power source, additional switching means for establishing dynamic braking connections for the motor, a controller for controlling the operation of said switching means, said controller being actuated from a braking position through coasting and accelerating positions in sequential relation to accelerate the motor and from an accelerating position through the coasting and braking positions to decelerate the motor by dynamic braking, and an additional controller for increasing the dynamic braking effect.

3. In a motor control system, the combination with a motor and a source of p ower therefor, of switching means for connecting the motor to the power source, additional switching means for establishing dynamic braking connections for the motor, a controllerfor controlling the operation of said switching means, said controller being actuated from a braking position through coasting and accelerating positions in sequential relation to accelerate the motor and from an accelerating position through the coasting and braking positions to deceleratethe motor by dynamic braking. and an additional controller cooperating with said first-named controller to increase the dynamic braking eect.

4. In a motor controlsystem, the combination with a motor and a sourceof power therefor, of switching means for connecting the motor to the power source, additional switch means for es tablishing dynamic braking connections for the motor, a controller for controlling the operation of said switching means, said controller being actuated from a braking position through coasting and accelerating positions in sequential relation to accelerate the motor and from an accelerating position through the coasting and braking positions to decelerate the motor by dynamic braking, and an additional controller cooperating with said rst-named controller to increase the dynamic braking eiIect said additional controller being operated independently of the iirst-named controller.

5. In a motor control system, the combination with a motor and a source of power therefor, of switching means for connecting the motor to the power source, additional switching means for establishing dynamic braking connections for the motor, a controller for controlling the operation of said switching means, andan additional controller cooperating with` the ilrst-named controller to vary the dynamic braking effect.

6. vIn a motor control system, the combination withtea'motor and a source of power therefor, of swithing means for connecting the motor to the powerfsource, additional switching means for establishing dynamic braking connections for the motor, a resistor for controlling the motor current, switches for shunting the resistor, relay means for controlling the operation of the resistor shunting switches, a controller i'or controlling the operation of said switching means. and an additional controller for changing the setting of said relay means to vary the braking ei.'-

fect. l

7. In a motor control system, the combination with a motor and a source of power therefor, of switching means for connecting the motor to the power source, additional switching means for establishing dynamic braking connections for the motor, a resistor for controlling the motor current, switches for shunting the resistor, relay means for controlling the operation of the-resistor shunting switches, a controller for controlling the operation of said switching means, and an additional controller for changing the setting of said relay means to vary the braking ei-` fect, said relay means being disposed to deenergize the operating coils of said resistor shunting switches upon the completion 'of a sequence of operation.

BASCUM O. AUSTIN. 

